An Investigation of the Population Dynamics of Atlantic Menhaden (Brevoortia tyrannus)

1985 ◽  
Vol 42 (S1) ◽  
pp. s147-s157 ◽  
Author(s):  
R. L Reish ◽  
R. B. Deriso ◽  
D. Ruppert ◽  
R. J. Carroll
Keyword(s):  
Population Dynamics ◽  
Environmental Variables ◽  
Atlantic Menhaden ◽  
Ekman Transport ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Brevoortia Tyrannus ◽  
Ricker Model ◽  
Dependent Growth ◽  
Special Case

The following biological components concerning the population dynamics of Atlantic menhaden (Brevoortia tyrannus) were investigated: growth, natural mortality, migration, fishing mortality, and recruitment. We found that a hypothesis of density-dependent growth is strongly supported by the data and that the dependence of growth on abundance appears to occur prior to recruitment. Age-specific natural mortality estimates seem biologically reasonable, except the estimate for age 1 menhaden, which appears to be too low. Most of the estimated migration probabilities also seem to be biologically reasonable, especially during the summer season for age 2 fish. Estimated age-specific fishing mortality rates demonstrate the increased fishing pressure on age 3 and younger fish since the early 1960's. When the environmental variables (temperature and Ekman transport) are excluded from the spawner–recruit analysis, then the Beverton–Holt model fits as well as other models examined, and it is the only model that is significant at the 0.05 probability level. Of the environmental variables examined, only westward Ekman transport in the South Atlantic region shows a relationship with recruitment. The unnormalized gamma function, which includes the Ricker model as a special case, is more responsive to the inclusion of westward Ekman transport than the Beverton–Holt model.

Influence of errors in natural mortality estimates in cohort analysis

1997 ◽  
Vol 54 (7) ◽  
pp. 1608-1612 ◽  
Author(s):  
G Mertz ◽  
R A Myers
Keyword(s):  
Mortality Rate ◽  
Similar Pattern ◽  
Cohort Analysis ◽  
Transient Behavior ◽  
Natural Mortality ◽  
Exact Formulation ◽  
Fishing Mortality ◽  
Bias Factor ◽  
Special Case ◽  
Mortality Estimates

The accuracy of the estimation of cohort strength from catch data may be greatly degraded if a poor estimate of the natural mortality rate is entered into the calculation. A straightforward, exact formulation for the error in cohort reconstruction due to a misspecified natural mortality rate is presented. The special case of constant fishing mortality is particularly transparent, allowing the error to be segmented into easily interpreted terms. A change in the fishing mortality may result in a distinct hump in the transient behavior of the bias factor, rather than a simple monotonic adjustment. This implies a similar pattern in estimated cohort strength.

A Method of Estimating Mortality Rates from Change in Composition

1962 ◽  
Vol 19 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Robert H. Lander
Keyword(s):  
Population Size ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Numerical Example ◽  
Final Population ◽  
Special Case

This paper examines the problem of estimating mortality rates from knowledge of catch and of the change in composition caused by selective fishing on one of two classes of a closed population.Estimators of fishing mortality in the presence and in the absence of natural mortality are given. An estimator of natural mortality is shown for the special case where final population size is known.A numerical example illustrates the method. Certain problems are discussed and two types of application are suggested.

scholarly journals A critique of the balanced harvesting approach to fishing

2015 ◽  
Vol 73 (6) ◽  
pp. 1640-1650 ◽  
Author(s):  
Rainer Froese ◽  
Carl Walters ◽  
Daniel Pauly ◽  
Henning Winker ◽  
Olaf L. F. Weyl ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Empirical Evidence ◽  
Negative Impact ◽  
Relative Size ◽  
Fish Populations ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Policy Changes ◽  
Ecosystem Models ◽  
Natural Productivity

Abstract The approach to fisheries termed “balanced harvesting” (BH) calls for fishing across the widest possible range of species, stocks, and sizes in an ecosystem, in proportion to their natural productivity, so that the relative size and species composition is maintained. Such fishing is proposed to result in higher catches with less negative impact on exploited populations and ecosystems. This study examines the models and the empirical evidence put forward in support of BH. It finds that the models used unrealistic settings with regard to life history (peak of cohort biomass at small sizes), response to fishing (strong compensation of fishing mortality by reduced natural mortality), and economics (uniform high cost of fishing and same ex-vessel price for all species and sizes), and that empirical evidence of BH is scarce and questionable. It concludes that evolutionary theory, population dynamics theory, ecosystem models with realistic assumptions and settings, and widespread empirical evidence do not support the BH proposal. Rather, this body of evidence suggests that BH will not help but will hinder the policy changes needed for the rebuilding of ecosystems, healthy fish populations, and sustainable fisheries.

A Stochastic Population Model for Managing the Atlantic Menhaden (Brevoortia tyrannus) Fishery and Assessing Managerial Risks

1985 ◽  
Vol 42 (8) ◽  
pp. 1371-1379 ◽  
Author(s):  
D. Ruppert ◽  
R. L Reish ◽  
R. B. Deriso ◽  
R. J. Carroll
Keyword(s):  
Population Model ◽  
Atlantic Menhaden ◽  
Juvenile Growth ◽  
Fishing Mortality ◽  
Brevoortia Tyrannus ◽  
Estimation Errors ◽  
Age Dependent ◽  
Stochastic Recruitment ◽  
Stochastic Population Model

A model including an age-structure, a stochastic egg-recruitment relationship, density-dependent juvenile growth, age-dependent fishing mortality, and fecundity dependent upon size as well as age was used to investigate three types of harvesting strategies: constant yearly catch policies, constant fishing mortality rate policies, and "egg escapement" policies, which are defined in the article. Because of stochastic recruitment, constant yearly catch policies appear unsuitable for managing Atlantic menhaden (Brevoortia tyrannus). Both other types of policies are suitable, but the egg escapement policies have higher long-term average catches. Using decision theory, we investigated risks due to the randomness of recruitment and to the estimation errors for the biographical parameters in our model. The risks appear to be acceptable.

scholarly journals A study of brown-marbled grouper (Epinephelus fuscoguttatus) population dynamics in Takabonerate National Park Waters, South Sulawesi, Indonesia

2021 ◽  
Vol 22 (10) ◽  
Author(s):  
FATMA FATMA ◽  
ACHMAR MALLAWA ◽  
NAJAMUDDIN NAJAMUDDIN ◽  
MUKTI ZAINUDDIN ◽  
FACHRIE REZKA AYYUB
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Mortality Rate ◽  
National Park ◽  
Size Structure ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
South Sulawesi ◽  
Exploitation Rate ◽  
Epinephelus Fuscoguttatus

Abstract. Fatma, Mallawa A, Najamuddin, Zainuddin M, Fachrie R. 2021. A study of brown-marbled grouper (Epinephelus fuscoguttatus) population dynamics in Takabonerate National Park Waters, South Sulawesi, Indonesia. Biodiversitas 22: 4298-4307. Understanding aspects of the population dynamics of groupers such as the brown-marbled grouper can provide valuable insights into how to manage grouper stocks effectively. Conducted from February 2020 to February 2021 in Takabonerate National Park waters, Selayar Islands District, South Sulawesi, Indonesia, this study sought to elucidate the size structure and cohorts, population growth rate, total mortality rate, fishing mortality rate, natural mortality rate, exploitation rate and yield per recruit (Y/R) of the brown-marbled grouper. Grouper samples were caught using several fishing gears (i.e., hand line fishing, spearfishing, and trapping) with a total catch of 1042 specimens. The sampled specimens exhibited significant size structure and were classified into five age-specific cohorts. The growth rate coefficient was 0.46/year, with the brown-marbled grouper population tending to exhibit slow growth (K < 0.5/year). The estimated asymptotic length was 109.0 cm. The fishing mortality was higher than the natural mortality, with an exploitation rate of 0.65, indicating that brown-marbled groupers in the waters of Takabonerate National Park have been subjected to extensive and intensive fishing, as also indicated by an estimated Y/R lower than the optimum Y/R rate.

scholarly journals POPULATION DYNAMICS OF TUNA (EUTHYNNUS AFFINIS, CANTOR 1849) IN WESTERN WATERS OF SOUTH SULAWESI

2020 ◽  
Vol 8 (8) ◽  
pp. 164-172
Author(s):  
Budiman Yunus ◽  
Suwarni ◽  
Basse Siang Parawansa
Keyword(s):  
Population Dynamics ◽  
Mortality Rate ◽  
Age Groups ◽  
Total Mortality ◽  
Assessment Tools ◽  
Natural Mortality ◽  
Age Group ◽  
Fishing Mortality ◽  
Growth Coefficient ◽  
South Sulawesi

This study aims to determine the population dynamics of tuna including age group, growth, mortality, exploitation rate and yield per recruitment. It was conducted from June to August in West Waters of South Sulawesi. By method of age group using Bhattacharya method with FAO-ICLARM Fish Stock Assessment Tools II (FISAT II) program, growth using Von Bertalanffy’s equation, natural mortality (M) using Pauly’s empirical equation, total mortality (Z) using Beverton and Holt’s equations, fishing mortality (F) by the formula Z = F + M, exploitation (E) using Baverton and Holt’s equations and yield per recruitment (Y/R’) using Baverton and Holt’s equations. The results of research of tuna observed were 737 includes 355 male tunas and 382 female tunas. The estimation of total length ranging from 215 mm to 429 mm. Male tunas are classified into 4 (four) of age groups with a length of 236.67, 272.8, 326.04 and 375.53 mm, respectively. Asymptote length (L∞) = 455.00 mm, growth coefficient (K) = 0.33 and theoretical age (t0) of -0.2377 per year. Total mortality rate (Z) = 1.12 per year. Natural mortality (M) = 0.41 per year, fishing mortality (F) = 0.71, exploitation (E) = 0.63 and yield per recruitment (Y/R’) = 0.0691, while male tunas are classified into 5 (five) of age groups with a length of 235.73, 272.86, 326.89, 360.89 and 408.89 mm, respectively. Asymptote length (L∞) = 453.50 mm, growth coefficient (K) = 0.42 and theoretical age (t0) of -0.1853 per year. Total mortality rate (Z) = 1.35 per year. Natural mortality (M) = 0.48 per year, fishing mortality (F) = 0.87, exploitation (E) = 0.64 and yield per recruitment (Y/R’) = 0.0784. Thus, it can be concluded that tuna in West Waters of South Sulawesi have declined and thought occur overfishing.

scholarly journals Population Dynamics and Stock Assessment of Gudusia chapra (Hamilton-Buchanan) in the Rajdhala Reservoir, Netrakona, Bangladesh

2007 ◽  
Vol 19 (3) ◽  
Author(s):  
M. A. RAHMAN ◽  
M. M. HAQUE
Keyword(s):  
Population Dynamics ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Length Frequency ◽  
Recruitment Pattern ◽  
Pattern Maximum

Population dynamics and stock assessment of chapila (Gudusia chapra, Hamilton-Buchanan) in the Rajdhala reservoir, Netrakona, Bangladesh was studied from January 2003 to December 2004 using length-frequency based analysis of FiSAT software to evaluate the growth parameters, mortality rates, exploitation rates, recruitment pattern, maximum sustainable yield (MSY) and the corresponding fishing mortality at this level. The annual rates of natural mortality, fishing mortality and total mortality were 1.34, 1.37 and 2.71 yr-1 in 2003 and 1.37, 1.58 and 2.95 yr-1 in 2004 respectively. The study revealed that the fishes were recruited in the fishery twice a year and the fishes were harvested at a higher level than the optimum fishing pressure. Twenty four percent of the present exploitation pressure on chapila is suggested to be reduced to get the MSY of this fish from the reservoir.

Virtual Population Analysis (VPA) Equations for Nonhomogeneous Populations, and a Family of Approximations Including Improvements on Pope's Cohort Analysis

1986 ◽  
Vol 43 (12) ◽  
pp. 2406-2409 ◽  
Author(s):  
Alec D. MacCall
Keyword(s):  
Mortality Rate ◽  
Population Analysis ◽  
Seasonal Pattern ◽  
Cohort Analysis ◽  
Natural Mortality ◽  
Close Approximation ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Special Case

A set of "backward" virtual population analysis (VPA) equations relates catch (Ct) from continuous fishing between times t and t + 1 to population n size (Nt, Nt+1) when a portion of the stock is unavailable to fishing. The usual VPA equations become a special case where the entire stock is available (i.e. the stock is homogeneous). A close approximation to the VPA equations is Nt = Nt+1 exp(M) + CtM/(1 − exp(−M)), which has properties similar to Pope's "cohort analysis" and is somewhat more accurate in the case of a continuous fishery, especially if the natural mortality rate (M) is large. Much closer simple approximations are possible if the seasonal pattern of catches is known.

Movement, Growth and natural mortality rate of the Red Spot King Prawn, Penaeus longistylus Kubo, from the Great Barrier Reef Lagoon

1990 ◽  
Vol 41 (3) ◽  
pp. 399 ◽  
Author(s):  
MCL Dredge
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Great Barrier Reef ◽  
Annual Variation ◽  
Growth Parameters ◽  
Natural Mortality ◽  
Barrier Reef ◽  
Fishing Mortality ◽  
Nursery Areas ◽  
Reef Lagoon

Movement, growth and natural mortality rate of the red spot king prawn, Penaeus longistylus, occurring in waters of the Great Barrier Reef off Townsville, Queensland, were investigated in a series of tagging experiments. Adult P. longistylus did not migrate after leaving nursery areas. Their growth rate was slower than that of the conspecific species P. plebejus, and significant inter-annual variation in growth parameters was observed. The natural mortality rate, assessed by sequential tagging experiments that eliminated the possibility of confounding with the rate of fishing mortality, was estimated to be 0.072 (week-1).

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